The present invention relates to a method for measuring (analyzing) a multiple-phase fluid flowing through a pipe, the fluid comprising a liquid phase in contact with a surface of the pipe and a gas phase located away from the surface covered by the liquid.
In order to optimize the production and lifetime of hydrocarbon producing operations, it is known to use a multiple-phase flow meter which allows the proportions of liquid and gas in a pipe of the installation, for example located at the outlet of a production well, to be determined regularly.
The data supplied by the measurement are used by the operators of the installation, especially in order to adapt the separation conditions of the phases of the multiple-phase fluid.
To that end, the flow-rate measurement has to be accurate (plus or minus 5% of the flow rate for each phase), non-destructive, reliable and independent of the type of flow regime flowing through the pipe.
In order to measure the phase fractions, it is known to use an instrument employing a radioactive source, which has a number of disadvantages in terms of storage, transportation and use.
In order to overcome that problem, there is known from the article by Hilland in Meas. Sci. Technol. 8 (1997) pages 901 to 910 a method for measuring a multiple-phase fluid flowing through a pipe with the aid of a coaxial probe, the end of which is placed in contact with the fluid.
The fluid is illuminated by the coaxial probe with the aid of an electromagnetic wave, and the admittance is measured at the interface between the probe and the fluid. The permittivity of the fluid and its composition are then calculated.
In order to operate the system, it is necessary to calibrate the probe with the aid of at least three reference solutions and then use an empirical model. The accuracy of the measurement is therefore not wholly satisfactory.